Avalanche Report for Creag Meagaidh

Issued

Avalanche Hazard Forecast

FOR PERIOD 18:00 Thu 25/12/2014 TO 18:00 Fri 26/12/2014

Hazard level
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Low
Human triggered avalanches not likely. Generally safe travel conditions.
Moderate
Human triggered avalanches are possible, so good visibility and good route selection is important, especially in steep locations as indicated in the reports. Groups should be managed carefully, keeping good spacing between people to reduce loading on slopes.
Considerable
Natural avalanches may occur - and a single person load is likely to trigger an avalanche on some slopes. Good visibility and route finding in mountain terrain is important, as is experience in avalanche hazard evaluation.
High
Natural avalanches will occur - and a single person load will trigger an avalanche on some slopes. Good visibility and good route-finding in mountain terrain is essential, as is experience in avalanche hazard evaluation.
Very High
Widespread natural avalanches will occur - and a single person load will trigger an avalanche on most slopes. Good visibility and good route-finding in mountain terrain is essential, as is experience in avalanche hazard evaluation.
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The avalanche hazard will be Considerable

Forcasted Snow Stability & Avalanche Hazard

Instability will persist in deeper windslab deposits mainly on North East to South East aspects above 800m. Most affected areas will be steep gully exits and the top of coire backwalls. Recently formed cornices will overhang many of these locations. Much better stability at lower altitudes on all aspects and on all recently wind scoured slopes. The avalanche hazard will be Considerable

Forcasted Weather Influences

Dry and cold throughout with light variable winds.

Key Snow Stability Observations

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Observed Avalanche Hazard -

The avalanche hazard is Considerable

Observed Weather Influences

Snow showers and wind died out overnight leaving Christmas Day cold, clear, bright and calm.

Observed Snow Stability and Avalanche Hazard

Accumulations of deep and marginally bonded windslab lie on most North East to South East aspects above 800m. Below 700m the snowpack is either sparse and scoured, or refrozen, crusty and stable. New cornices hang over steeper recent lee slopes. The avalanche hazard is Considerable

Comments

Excellent general cover above 700m with deep drifts above 800m. Treacherous and tiring crust below 700m.

Weekly Snowpack Summary
  
  • Storm snow to start the period resulted in soft weaker layers overlaid by hard more dense deposits. Temperature fluctuations followed mid week with a thaw to all level by end of the week. The depleted snowpack is generally now well consolidated. NB Some cornice collapses mid period with new build up on-going.

    A week of persistent thaw with occasional snow showers and cooler interludes. Snow pack now much patchier and what remains characterised by coarse-grained, stable structure. Deep glide cracks and crevasse-like features present as well as partially collapsed old cornice lines.

    Slow steady thaw conditions and stable for most of the period with freezing levels above summits occasionally lowering just below. Bright sunshine briefly mid-period with some sun on snow localised instabilities, glide cracks continue to develop with remnants of cornices slumping and collapse prone. Slow thaw persisting to end period.

    New snowfall at high levels to start the period were followed by very strong winds with heavy drifting and the rapid slab build up of unstable slab from re-distributed snow. Poor stability with avalanches (class 2 & 3 events)followed these accumulations mid period on NE and E aspects around 900m. Warmer temps and strong sunshine followed with localised wet snow instabilities & cornice debris. A re-freeze now has resulted in much better stability - a few instabilities above 900m from new showers.

    More frontal activity coming in from the Atlantic with rain, very strong winds and mild temperatures; colder, wintry towards the end of the week. Snowpack generally moist and stabilising but diminished in thaw. Snow line now 750 to 800m. Most large cornices now down but some remain. Full depth glide cracks in several never seen before locations: all continue to widen. Colder temps encouraging MF crust to form with new windslab developing on N to E aspects above 850m.

    Two thaw cycles have affected the snowpack over the period with associated wet snow avalanches and a number of cornice collapses primarily on North West through North to East facing slopes. Between these cycles regular snow showers mostly above 700m brought new snow instabilities with drifted accumulations. Some deep seated weaknesses persist within accumulations above 900m.

    Lots of avalanche activity to start the period with numerous large events from a temperature rise accompanied by rain on snow, all mostly below 800m, in some cases these ran to full depth on North through North East and Easterly aspects and involved significant volumes of wet snow. Cooler temps mid week brought some consolidation. New snow showers continuing to build slab again at highest elevations above 900m on same aspects to end period. Good consolidation at lower elevations

    Frequent frontal activity brought snow then warm sector conditions throughout the week. Pattern as follows: initial dry snow instability then transitional wet snow instability followed by a period of consolidation. Avalanche activity has been both dry and wet varieties. Some of the massive and commonplace cornices collapsed in the last wet-warm cycle. Large and deep full depth avalanche on 17th-18th at 750m on a ESE aspect of Sron a Ghoire.

    Blizzard conditions to start the period gave rise to lots of snow transport at high levels. This was followed by avalanche activity (temp rise)primarily NE & E aspects - inner Coire Ardair , although due to cross-loading on high, sheltered areas some activity also noted on SE aspects. Mid-week strong, mostly SE winds and regular snow showers maintained areas of poorly stabilised slab above 850/900m,a cooler period delivered snow to all levels mid-week. Strong mostly SE/SW winds throughout. Highs

    Fresh snowfall followed by some high avalanche activity at the start of the period with several events in Inner coire Ardair NE through E aspects. Further snowfall through the period maintained areas of poorly stabilised slab which became more widespread in variable winds. A feature throughout has been the high level nature of the instabilities and whilst some run out zones affected terrain down to 700m the hazard remained for the most part high on slopes above 900m.

    Snow showers above 800m throughout accompanied by mostly SE winds. Good cover in high plateau areas with pockets of harder windslab around coire rims with new cornice development. Snowpack fairly well consolidated at lower elevations. Snow lie towards end of week with fresh showers and new soft slab NW aspects. Cooler FL around 500m

    A showery and predominately SW airflow over the period. Very little snow lying below 800m but above this regular showers have added to areas of windslab mainly lying at very highest elevations above 900m on N through to E aspects. FL levels seldom rising above summits or lowering below 400m. Greatest additions of new snow towards end of period with heavy snow showers on tops - but still only bringing a dusting below 800m. Thaw to summit with rain forecast to end week.

    Sequence of snow showers throughout with drifting, then colder temperatures. Significant windslab build up followed by milder temperatures and consolidation. Cool temperatures followed with little snowfall continuing the stabilising trend within the snowpack. Snowpack is currently moist and well stabilised in all locations. Large old cornices above some very steep locations.

    Periods of snowfall with windslab development, followed by melt/freeze conditions saw snow avalanche activity before and after thaw. Some of the avalanches cornice triggered. One or two small full depth avalanches during thaw on very steep ground. Snowpack currently moist with a surface crust at higher altitudes and humid windslab confined to locations above 1050m on N to E aspects.

    Fluctuating temperatures helping to consolidate existing snowpack. Strong South westerly's throughout bringing snow showers to highest elevations only, with any new snow weaknesses and windlslab accumulations confined primarily to NW to E facing gully tops and exits above 850m and around coire rims. Localised Considerable for much of period.

    Strong SW throughout with some frequent snowfalls (some very heavy) Temperatures fluctiating althoufh remaing below summit levels. Weakness in windslab accumulations persisting at highest elevations. Deep drifts at lower levels with breakable crust towards end of week below 750m. Little activity in coires - good cover above 750m. Ice forming in usual watercourses. Some cornices beginning to build above Easterly aspects with avalanche activity mostly cornice / some soft slab triggered on E aspect

    Patchy snowpack to start then a stormy week with periods of snowfall and drifting particularly near end of period. New snow instability in thinner windslab noted but this improved with milder temps. Deeper windslab later with notable new snow instability due to rapid build up.

    Sparse and patchy snowpack with larger patches only above 850m. Some South to South East facing coire rims hold a little more old snow. Thawing at all levels.

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